Floor or roof construction



July 25, 1939. M. G. HILPERT FLOOR OR ROOF CONSTRUCTION Fi-led Feb. 5,1937 -4 Sheets-Sheet 1 0000 0000000000 IW o iObovtvOrfto.

Me ier GeaH/ZPGWL July 25, 1939. M, Q HlLPE'RT 2,167,208

FLOOR 0R ROOF CONSTRUCTION Filed Feb. 3, 1937 -l 4 Sheets-Sheet 2 Meier.Gol faerf `luly 25, w39c M. G. HILPERT FLOOR OR ROOF CONSTRUCTION FiledFeb. s, 1937 4 sheets-sheet 3 Mei/e GGILH-perl;

, July 25, 1939. M. G.`H|| PERT FLOOR 0R ROOF CONSTRUCTION Filed Feb. 3,1957 4 Sheets-Sheetl 4 l Mierbmfligpert,

Patented July 25, 1939 UNITED STATES PATENT OFFICE 18y Claims.

This invention relates to improvements in floor and roof structures ofthe type which include steel beams to support the principal loadings,and has particular reference to the construction intermediate of andabout said beams.

One important object of the invention is to provide a strong,light-Weight oor or roof construction intermediate of and about theprincipal load supporting steel beams thereof, which constructionmaterially assists said beams in carryving live loads and serves toreinforce said beams against deflections. j

Another important object of the invention is to provide a floor or roofconstruction intermediate of and aboutlthe principal load supportingsteel beams thereof, which construction serves eifectively to fire-proofsaid beams and may readily be made to meet the nre-proofing requirementsof 'various different building codes.

2g Another important object of the linvention is to provide a floor orroof construction intermeiiiate of and about the principal loadsupporting -beams thereof, which construction includes a major number ofisolated air spacesf of major size consistent with the depth orthickness and required strength of the floor or roof, affording', inthemselves, effective vthermal and sound insulation and being designedto accommodate bulk or other insulating material to afford additionalinsulation in any desired case.

Another important object of the invention ls to provide ajoor or roofconstruction intermediatefof and about the principal load supportingbeams thereof, whichconstruction is cheap and easy to produce and may beproduced either in situ, or, in major part, as low cost pre-fabricatedunits capable of rapid and easy installation in a building structure.

With the foregoing and various other objects and purposes in View, whichwill become more fully apparent as the nature of the invention is betterunderstood, the same consists in the various novel features ofconstruction, combination and arrangement as will be hereinafter morefully described, illustrated in the accompanying drawings and defined inthe appended claims.

In the drawings, wherein like characters of reference denotecorresponding parts in related Views:

Figure l is a top plan View illustrating an in situ embodiment of thepresent licor or roof construction, parts being broken away to show theunderlying construction.

Figure 2 is a longitudinal section through the 5s construction shown inFiel.

Figure 3 is a transverse section through the construction shown in Fig.1.

Figure 4 is a detailperspective view illustrating a beam carriedreinforcement for bonding in the plastic material adjacent tothe beam.

Figure 5 isa View similar to Fig. 4 `illustrating an alternative form ofbeam carried reinforcement. y y

Figure 6 is a side elevation of the reinforcement means for one of thejoists.

Figures 7, 8 and 9 are detail sectional views illustrating alternativeforms of beams specially designed to be used with the presentpre-fabriecated construction intermediate and about the same. 16

Figure l0 is a View similar to Fig. l illustrating an embodiment of theinvention in'which the construction intermediate the principal load supeporting beams is comprised mainly by pre-formedV elements.

Figure 11 is a longitudinal section through the construction shown inFig. 10.

Figure 12 is a transverse section on the line I2-I2 of Fig. 10.

Figure 13 is a detail longitudinal section illustrating an alternativeform of end piece which may be used in the pre-formed elements; and

Figures 14 and 15 are views similar to Figs. 12 and 11 respectively,illustrating anl alternative form of joist which may be used in lieu ofthe joists illustrated in Figs. 1 to 12.

Figure 16 is a perspective view of the improved unit of construction. l

In modern building structures having steel frames it is usual to providesteel floor and roof 3.5 beams to support the' principal floor and roofloadings. Usually these beams are ofthe I-beam type and extendhorizontally,A or substantially horizontally, in parallel, spacedrelationship between columns or walll beams to vwhich they are securedat their ends. The accompanying drawings illustrate a pair of suchbeams, designated as I0, I D, disposed horizontally in spaced, parallelrelationship. However, as will' later become apparent, it is notnecessary that said beams be disposed either horizontally or parallel,as the present floor or roof construction is readily capable of beingformed between them whether they slope or are inclined to the horizontaland whether they are or are not disposed parallel to each other.

In carrying out the present invention there are provided a suitablenumber of reinforced concrete joists Il to extend between the beams l0.These joists Il are preformed either at the building site or at anyother suitable location,

and each includes a concrete body of preferably vertically elongated,rectangular shape in cross section having embedded therein a suitablereinforcing steel frame comprising, for example, an angle iron tensionmember I2 disposed near the bottom of the joist and extendinglongitudinally thereof, a compression member I3 in the form of a rod orthe like disposed near the top of the joist and extending longitudinallythereof, and a plurality of upright rods or the like Il connecting themembers I2 and I3 at points suitably spaced therealong. Conveniently,certain of the uprights I4 may be extended laterally at their lower endsthrough holes formed in the upright flange of the tension member I2 andmay be Welded to said tension member, and near their upper ends may bewelded to the compression member I3. However, any or all of saiduprights I4 may be secured to the members I2 and I3 in any othersuitable or desired manner. Moreover, all or some of said uprightsextend short distances above the top of theeompleted joist and some mayextend below the bottom of the completed joist for purposes which willlater appear.

The joists I I obviously are capable of easy and economical production,either singly or in pluralities, in suitable forms or molds. They areformed with downwardly and outwardly inclined ends and with upwardly andoutwardly inclined bottoms adjacent to their ends so that when they aresubsequently disposed between the beams Il) with their ends resting uponthe laterally extending bottom ilanges of said beams in accordance withthe invention, their bottom faces are disposed flush, or substantiallyflush, with the bottom faces of said beams andspaces for the receptionof concrete, aerocrete Yor the like are formed between their ends andthe webs of said beams. In producing said joists suitably symmetricalopenings I5 are formed Ytherethrough to accommodate conduits forAelectrical wiring or the like when the joists are embodied in abuilding.

According to the in situ embodiment of the invention illustrated inFigs. 1 to 3, a series of the joists II are placed between the beams Iin suitably spaced apart, preferably parallel relationship and arecovered by expanded metal lath or similar material I6 which extendsacross the tops of the spaces between said joists. At its sides thismaterial I6 is extended downwardly, as indicated at Il, over thedownwardly and outwardly inclined ends of the joists II and across thespaces between the joists to points such that, when concrete or the likeis poured between the webs of the beams I0 and the metal lath, theconcrete or the like will spread out over the bottom flanges of thebeams and to either side of the joists and, upon hardening, willireproof the lower flanges of the beams and serve at the same time tofix the joists inspaced relationship. The upper ends of the uprights I4extend through the material I6 and some of them are bent downwardly uponsaid material to hold it securely in place.

Beneath the joists II and the beams II) is arranged a ceilingreinforcement in the form of relatively light weight metal ceiling lathI8 or other suitable material which extends 'across the bottoms of thespaces between said joists and beams and is secured thereto in anysuitable manner, as, for example, by means of tie wires I9 or by havingbent upwardly Vther'eagainst the lower ends of such of the uprights I4as extend below the joists.

After the joists I I have been placed in position between the beams IUand the materials I6 and I8 have been placed in the positions describedrelative to said joists and beams, flooring or roofing concrete, Hayditecr the like, designated as 25J, is poured into the spaces between thebeams I and the downturned side portions of the material IS, and alsoover the top of the material I6 and over the tops of the beams Ill toany suitable or desired depth, some of the concrete, Haydite or the likeflowing over the bottom anges of the beams I and thus fireprooflng saidbottom flanges and fixing the joints in place as previously stated.Previously, or at any desired time, suitable ceiling forming material,such as plasterboard or preferably a plaster mortar, designated as 2|,is applied to the lath or similar material I8. Thus, there is formed afloor or roof construction of hollow or cellular form having sound andthermal insulating qualities in itself and which may have beenadditionally insulated, had that been desi-red, by placing bulkinsulation or insulation of any other desired type within the air spacesor cells thereof prior to covering said air spaces or cells b-y thematerial I6. Moreover, due to the beams I!! being completely encased bythe materials 2-0 and 2l, they Vare effectively reproofed and may befire-proofed to any desired extent in conformity with any given buildingcode simply by varying the thicknesses of the materials 20, ZI.Furthermore, the material 26, when set and bonded to the joists I I bythe uprights I4 and the material I6, not only serves to prevent lateraldeflections of thebeams I0, but provides, in itself, an effectiveconcrete T-beam cooperating withthe beams I0 to provide a composite beamwhich is exceptionally 'eifective to sustain loads to which the floor orroof may be subjected. Also, it is obvious that by having-the topportions of some or all of the uprights I4 bent over into the flooringor roofing material 2B, the necessary bonds are provided to makeeffective composite T-beams -of the joists and the flooring o-r roof-lng26. Furthermore, since the ends of the joists are firmly embedded in thematerial 20 and consequently are rigid with respect to the beams I0, itis evident that said joists in conjunction with the material 2l! willcarry additional loads due to the arch actions from the bottom flangesof the beams I0 through the joists and the material 2D. Also, since thematerial 20 ows to either side of the ends ofthe joists and therebystays the joists against Ylateral movement, the entire construction,panel by panel between beams IIl and subpanel by sub-panel betweenjoists, becomes one integral construction capable of supporting heavierloads for the materials used than if the beams and joists operatedsingly.

While it is not essential that the beams I0 have top elements inaddition to their top flanges for embedment in the material 20 toreinforce said beams, it is, nevertheless, desirable to provide vsaidbeams with such elements. In this connection, Figs. 3, 4 and 5illustrate that crimped rods 22 are welded to and extend from the websof the beams Ill upwardly and outwardly across the edges of the topflanges of said beams, to which flanges they also are welded, and thatsaid rods have welded thereto, outwardly of the outer edges of the topflanges of said beams,'other rods 23 extending longitudinally of saidbeams for embedment in the material 20 and for cooperation with the rods22 to reinforce the said beams by bonding with the material 2D encasingthe top portions of said beams and making composite T-beams thereof.Alternatively, and

as illustrated in Fig. 4 of the drawings, each beam I0 may be providedwith a single crimped rod 22a disposed flatly on top thereof and weldedthereto and having extending beyond the edges of the top ange of thebeam portions 221 to which are welded rods 23 similar to the rods 23. Infact, the beams I0 may carry any suitable means at their tops inaddition to their top anges for embedment in the material to reinforcesaid beams. Similarly, instead of applying a mortar or plastic material2| to the lath I8 and allowing said material to set, a plasterboard orpre-formed slabs of any suitable ceiling material may be employed andmay be secured in place in any desired manner, as, for example, bynailing the same to the joists Il,

' it being pointed out inthis connection that the base of the concretematerial comprising said joists and also the flooring or roong 20 may becinders or the like permitting the driving of nails into the same andaffording good sound insulating qualities. In any event, the ceilingmaterial 2l for in situ placement preferably has either a plaster baseor is in the form of a good commercial plasterboard so that anyfinishing coat, or coats, of plaster will eiectively adhere thereto.

Tne embodiment of the invention illustrated in Figs. 1 to 3 isparticularly adaptable to rapid and 'economical construction becausesuccessive beams I0 may be placed and supported in their final permanentpositions preparatory to construction of the floor proper between them.On the other hand, in some cases it may not readily be possible tooperatively position the joists I I between a pair of the beams l0,particularly if thel lowering the other end of the joist,or the otherside of the slab skeleton, as the case may be, into engagement with thebottom flange of the other beam. In this connection, Fig. '7 illustratesthat the top flange of eachbeam I0 may be` removed,

I either entirely or in part, at one side of the web of the beam,thereby to permit the joists Il, as embodied in a pre-formed slabskeleton, to readily be lowered into position in the manner stated torest upon the bottom flanges of said beams. As

. an alternative construction,- Fig. 8 illustrates that the beams I0 maybe of vinverted T-shape in section and may have narrow compressionmembers at their topsl formed by Welding rods 24 against opposite sidefaces of their webs. figure also suggests that an equivalentbeam may beformed by only partially removing the top flanges of an I-beam or ,byrecessing either or both top flanges at a point or points of leastmoment, to permit the joists first to be lowered onto the beam bottomanges and then to be slid along said bottom flanges to desired finalpositions. As a further alternative construction, Fig. 9 illustratesthat the beams I0 may be formed each from a channel section 25 having anangle 26 welded to its bottom to provide a bottom tension member ofinverted T-shape, and further having a rod 21 welded to the top thereoffor cooperation with the top flange to provide a compression member.Other beam constructions, of which the foregoing merely are examples,obvious- Thisl ly may be devised to aiord necessary strength and topermit the joists to be assembled therewith in the manner stated.Alternatively, the joists and lath materials if placed insitu, orprefabricated skeleton units, may be placed at one end on the bottomilange of beam I and this intermediate construction may be supported onhorses resting on the floor construction below and the adjacent floorbeam l0 may then be swung into its final position with its bottom flangebelow the said intermediate construction at its other end, after whichsaid joists or units may be lowered permanently onto the bottom flangeof the last placed beam I0.

As previously indicated, the present floor or roof' constructionintermediate the beams l0 may be comprised in major part by pre-formedslab skeletons corresponding in all essentials to the in situ slabskeletons formed by practicing the invention as described in connectionwith the illustration in Figs. 1 to 3. A construction embodyingpre-formed slab skeletons is illustrated in Figs. 10 to 13 and will beobserved to comprise a plurality of-slab skeletons disposed in end toend relationship between the beams I 0. These skeletons may be of anysuitable length and are of a width determined by the spaced apartrelationship ofthe vbeams lll. As shown, eachv slab skeletonr comprisesany desired plurality of joists Ha which may be duplicates of the joistsI l and which may be disposed in any desired spaced apart, parallelrelationship. The two outermost joists of each slab skeleton are spacedinwardly from the ends of the slab skeleton and at the ends of the slabskeleton are'sheet Vmetal elements 28 having the profile or sideelevational shape of the joists Hato preserve the cross-sectional shapeof the slab skeleton at its ends and to cooperate with the correspondingelements at the ends of adjacent slab skeletons to provide forms for thepouring of joists between the ends of adjacent'slab skeletons. In thisconnection and as illustrated in Figs. 10 to 12, the elements 28 are ofchannel shape in cross section and have inwardly directed top and bottomilanges. Alternatively and as illustratedl in Fig. 13, said elements maybe of substantially Z-shape in cross section, each having an inwardlydirected ange at its top and an outwardly directed flange at its bottom.Alternatively, said elements may be of any other suitable sectionalshape. In any event, the joists l Ia and the elements 28, and the spacesbetween said joists and elements, are covered by expanded metal lath orthe like E63 which is extended downwardly over the downwardly andoutwardly inclined ends of said joists and elements and between the samemay be tucked inwardly to better preserve the spacing of said joists".Similarly, the bottoms of said joists and elements, and the bottoms Yofthe spaces therebetween, are covered by metal lath, wire mesh or thelikeV i8a fastened in place by tie tires ille or by the uprights Ma; Inaddition, stays orbraces 29 extend from the tops of alternate of thejoists and the elements 28 to the bottoms of the remaining joists andelements to hold the joists and the elements 28 properly'positioned andto impart rigidity to the slab skeletons.

Following fabrication of the slab skeleton they preferably are loweredinto 'a thin lay-er of' liquid cement and cinders or Haydit'e which,enmeshing the wire mesh Ia and'hardening, forms the ceiling plasterbase. Thus, such base, being applied underfactory conditions, will beofY economical thickness and uniform texture for its purpose.

gil

Obviously the width of such precast plaster base must register asdesired with the distance center to center of the supporting beams l andthe length must be of the exact length center to center` of the formedin situ joists designated as J.

This prefabricated skeleton or unit having a solidly supported base orbottom allows of adding under factory control the required thickness ofbulk or other type of insulation as indicated for the permanent positionin building of said prefabricated floor unit. The insulation may beintroduced through the ends between the joists under the downwardextending mesh la or by f lifting a central top section of the mesh laas previously arranged for. This factory introduction of the insulationeliminates a tedious operation under the many unfavorable conditionsobtaining when placing insulation between the beams at the building siteand expedite erection of the building proper. This prefabricated unitallows alternates as the substitution of commercial plasterboards or thelike in place of the factory cast plaster base, said board beingfastened to the underside of said joists Ila and to end members 28 and,if desired, being wired to the edges of the mesh |62. Such alternateswill cbviously provide the base desired for factory placing ofinsulation, for reproong the webs and bottom flanges of beams ll) andfor the'ceiling plaster finishing coats.

In constructing a iioor or roof by employing slab skeletons asdescribed, the slab skeletons are placed between the beams l0 in end toend relationship with the ends of the joists lla resting upon the bottomfianges of Vthe beams. In this connection, if end elements 28 asillustrated in Fig. 13 are used, the outwardly directed bottom flangesof said elements at adjacent ends of adjacent slabs are disposed inabutting relationship, thereby to close the bottoms of the spacesbetween the webs of said elements. On the other hand, if the elements 2Bdo not have outwardly directed bottom flanges, said elements are heldproperly spaced apart, and the spaces between them are closed at theirbottoms in any suitable manner, as for example, by means of a suitableextension of aV pre-cast plaster base Yheld in place by the wire mesh laor otherwise. In any event, after placing the slab skeletons between thebeams,

concrete, Haydite or the like is poured into the spaces between theelements 28 at adjacent ends of the slab skeletons, thereby forming anadditional joist at the adjacent ends of each' two adjacent slabskeletons. At the same time, con crete, Haydite or the like is pouredinto the spaces between the beams l0 and the downwardly directed andinwardly tucked side portions of the metal lath llia and over said metallath and said beams to a desired thickness or depthV with the sameadvantageous results as described in connection with Figs. 1 to 3 of thedrawings. Thereafter, or previously. if desired, the ceiling finishn ingcoating, or coatings, is, or are, applied. In this connection it will beunderstood, of course, that conduits 30 for electric wires or otherpurposes may be embodied in the slab skeletons either duringconstruction of the same or at any time thereafter and that connectionsbetween said conduits may be made in the spaces between adjacent ends ofthe slab skeletons prior to pouring of the concrete. It will also beunderstood that the joists formed between the ends of adjacent skeletonsections may be reinforced in any desired manner.

It is not essential'that the joists l or Ila be of the constructionheretofore described or even vof reinforced concrete construction. Onthe contrary, said joists may be of any suitable construction, and inthis connection Figs. 14 and l5 'illustrate one alternative constructionwhich may be especially desirable in certain installations. Asillustrated' in said figures, the joists, designated generally Vas l Ib,are of all metal construction and are characterized by Webs 30 formed ofrods which are crimped to provide successive V-shaped and invertedV-shaped formations as viewed in siderelevation. Such of said j oists asare intended to be used intermediate the ends of pre-formed slabskeletons preferably have top and bottom compression and tensionmembers, respectively, each of which is comprised by two pieces of angleiron 3| disposed to opposite sides of the web 3G, respectively, andwelded to the apices of the V- shaped formations of saidv web. On theother hand, such of said joists as are intended to be used at the endsof preformed slab skeletons may have top and bottom compression andtension members, respectively, each comprised by a single piece of angleiron at the inner side of the web of theAjoist. Alternatively, thebottom member may be comprised by two pieces of angle iron and the topmember by only a single piece of angle iron atv the inner side of theweb; 0r, the top member maybe comprised by a single piece of angle ironat the inner side of the top of the web and the bottom member may becomprised by a single piece of angle iron at the outer side of thebottom of the web. In this connection it is apparent that in any casewhere the bottom member consists of or includes a piece of angle iron atthe outer side of the web, the outwardly directed anges of adjacent slabskeletons cooperate to close the bottomY of the space between the slabskeletons. Obviously the joists illustrated in Figs. 13 and 14 may beused either individually in the manner described in connection with the`joists i! of Figs. l to 3, or in forming slab skeletons of thecharacter described in connection with Figs. 7 to 13. As shown, saidjoists are longer at their bottoms than at their tops. and when embodiedin slab skeletons the metal lath' or the like itl covering them and thespaces therebetween extends downH wardly over their ends as at 32 andalso over their sides, as at 33. In other respects said slabs and slabskeletons. and floors or roofs embodying the same are, or may be, of thesame construction set forth in connection with Figs. l to 3 and 7 to 13.

Any of the joists may be formed so that when they are seated at theirends on the bottom flanges of the beam Ill their top and bottom facesmay be disposed at any desired levels relative to the top and the bottomfaces of said beams. Moreover, in any case where the bottoms of the.ioists are disposed at elevations such that a ceiling coating of normalthickness applied thereto does not eifectivelycover the bottoms of thebeams l0, the said bottoms of said beams may be covered and effectivelyfireproofed byV a stepped ceiling formation as illustrated in Fig 14 andincluding, for example, a plank 34 of suitable insulating material, suchas gypsum, wired or otherwise secured against the bottom of each beam.

Without further description it is thought that the features andadvantages of the invention will vbe readily apparent to those skilledin the art,

and it will of course be understood that changes in the form, proportionand minor details of construction may be resorted to, without departingfrom the spirit of the invention and scope of the appended claims.

I claim:

l. In a building structure, spaced floor or roof beams, joists extendingbetween said beams, a plastic material supporting sheeting covering saidjoists and the spaces therebetween and partly covering the ends of saidjoists and the spaces between such ends, and plastic material disposedover said beams and said sheetingand extending downwardly between theends of said joists and the webs of said beams and `providing incooperation with said beams and joists a composite beam structure. v

2.` In a building structure, spaced floor or roof beams having webs andbottom flanges, joists extending between said beams and resting at theirends on the bottom anges thereof, the ends of said joists being spacedfrom the webs of said beams, a plastic material supporting sheetingcovering said joists and the spaces therebetween and extendingdownwardly over portions of the ends of said joists and over portions ofthe spaces between the ends of said joists, and plastic materialcovering said sheeting and said beams and extending into the spacesbetween the webs of the beams and the downwardly extending portions ofsaid sheeting.

3. In a building structure, spaced iioor or roof beams having webs andbottom anges, joists extending between said beams and resting at theirends on the bottom flanges thereof, the ends of said joists beingdownwardly and outwardly inclined, a plastic material supportingsheeting covering said joists and the spaces therebetween and extendingdownwardly over portions of the ends of Y said joists and over portionsof the spaces between the ends of said joists., and plastic materialcovering said sheeting and said beams and extending into the spacesbetween the webs of the beams and the downwardly extending portions ofsaid sheeting.

4. In ar building structure, spaced floor or roof beams having laterallyextending top and bottom compression and tension members, respectively,joists extending between said beams and supported thereon, a plasticmaterial supporting sheeting extending over said joists and over thespaces therebetween, and partly covering the ends of said joists and thespaces between such ends, the side marginal portions of said sheetingbeing directed beneath the top compression members of said beams inspaced relationship thereto, and plastic material covering said beamsand said sheeting and extending into the spaces between the topcompression members of said beams and the underlying marginal portionsof said sheeting.

5. In a building structure, spaced floor or roof beams having laterallyextending top and bottom compression and tension members, respectively,joists of reinforced concrete extending between said beams and supportedthereon, a plastic material supporting sheeting extending over said andextending into the spaces between the top compression members of saidbeams and the underlying marginal portions of said sheeting and havingthe aforesaid parts of the joist reinforcements embedded therein.

6. In a building structure, spaced oor or roof beams having webs andbottom flanges, joists extending between said beams and resting at theirends on the bottom flanges thereof, the ends of said joists being spacedfrom the webs of said beams, a plastic material supporting sheetingcovering said joists and the spaces therebetween and extendingdownwardly over portions of the ends of said joists and over portions ofthe spaces between the ends of said joists, and plastic materialcovering said sheeting and said beams and extending into the spacesbetween the webs of the beams and the downwardly extending portions ofsaid sheeting and downwardly over the bottom flanges of said beams.

7. The combination as set forth in claim 6 including ceiling lathmaterial secured against the bottoms of the joists and extending acrossthe bottoms of the spaces therebetween, and plastic ceiling materialextending across the bottoms of the beams and the joists and across thebottoms of the spaces between said beams and joists and having saidceiling lath material embedded therein.

8. 'Ihe combination as set forth in claim 6 including ceiling materialextending across the bottoms of the spaces between the beams and thejoists and cooperating with the plastic Inaterial covering said spacesto provide a hollow or cellular floor or roof structure.

9. The combination as set forth in claim 5 in which ceiling lath `andceiling material extend across the bottoms of the spaces between thebeams and the joists, and in which some of the joist reinforcementsextend below the joists and serve to fasten the ceiling lath to thejoists.

l0. The combination as set forth in claim 2 in which the beams have topAflanges and in which additional flange `members and composite beambonds for the plastic material are carried by and extend laterally fromthe top flanges of the beams and are embedded in the plastic material.

11,. A pre-fabricated unit for the reinforcement of floors, roofs andthe like formed from plastic material, said unit comprising laterallyspaced joists, and foraminous metal attached to said joists andextending across the space between the tops of said joists anddownwardly across the upper portions of the spaces between the ends ofsaid joists.

l2. A pre-fabricated unit for the reinforcement of floors, roofs and thelike vformed from plastic material, said unit comprising laterallyspaced joists, and upper and lower sheets of foraminous metal attachedto the tops and the bottoms of said joists and extending respectivelyacross the spaces between the tops and the ybottoms of said joists, thevend portions of the upper sheet extending downwardly across the spacesbetween the upper portions of the ends of the joists.

13. AA pre-fabricated unit for the reinforcement of hoors, roofs and thelike formed from plastic material, said unit comprising laterally spacedjoists the tops of which are shorterthan their bottoms, and metal lathextending across the tops and ends of said joists and across the spacebetween the tops and partly across the space between the ends of saidjoists and fastened to said joists.

14. A pre-fabricated unit for the reinforcement of floors, roofs and thelike formed from plastic material, said unit comprising at least onejoist intermediate the ends of the unit, sheet metal members at the endsof the unit having the side elevational shape lof the joist, and metallath material extending over saidv joist and said members and over `thespaces therebetween'.

15,7A pre-fabricated unit as set forth in claim 14 in which the sheetmetal members at the ends of the unit Ihave' outwardly directed bottomanges for cooperation with the companion flanges of adjacent units toclose the bottoms of the spaces between the end members of adjacentunits. s

16. A pre-fabricated unit for the reinforcement of oors, roofs and thelike formed from plastic material, said unit comprising a plurality ofspaced, parallel josts having downwardly and outwardly inclined ends,and metal lath material extending across the tops of said josts andacross aictgao

